"Adjusting the Intonation"?

[Mannyrock55]

Hey Guys,

I often see references, saying that folks had to "adjust the intonation" on their Guitar. What does this mean? I only adjust intonation by using the tuners.

My guitar has a block saddle, and I see that each block has a tension screw and spring inside of it, which would let you tighten or loosen the string by turning the screw. But, why is this necessary? Why would you care how far or close the end of the string is to the neck, since we are only talking about a quarter of an inch of adjustment? I have also seen references which say that this is done during a guitar set-up.

Thanks for all information.

Mannyrock

[Wonks]

You are not adjusting the intonation bu using the tuners, you are tuning the open string to a reference frequency.

You need to move the saddle (or thecwhole bridge in some instances) backwards or forwards so that at the 12th fret the first octave of the open note also plays in tune.

Various reasons.

It’s hard for manufacturers to get the bridge perfectly positioned. So the ability to move the saddles back and forth is certainly required. (I’ve recently tried setting up an older Vintage Les Paul style only to find the whole bridge was set about 4mm too far back).

Theres a small bit of the string at either end (nut or fretted position and bridge) that is a transition section between not vibrating and freely vibrating. This shortens the effective length of the string. The thicker the string, the longer this transition length is. It’s almost nothing on the top E, and maybe 2-3mm on the low E.

There are also variations in string path length depending on how the action is set up. The higher the action, the longer the path from the fretted position to the bridge. It’s not a huge increase, but it’s another little thing that adds to the string length which requires adjustment for.

Finger fretting pressure can also increase the string tension if you tend to press the strings down hard when you fret. This can obviously be variable depending if you are playing softly or loudly, so you need to try and fret at the 12th fret at your average pressure when setting the intonation.

in addition, strings are very rarely uniform along their whole length. Almost, but not quite. Small variations in mass/unit length can mean that you may need to intonate after each change of strings.

So you do need to set the intonation using the saddle adjustment screws.

Get the open string in tune, then fret at the 12th fret and see how in tune it is. If sharp, move the saddle back a not (a lot if very sharp). If flat, move the saddle forwards. Then retune the open string, fret at the 12th fret and check the tuning again. Adjust as necessary until the open string and 12th fret tunings are both correct.

[merlyn]

I don't think it's as complicated as Wonks is making out. On an acoustic guitar a bridge that has been adjusted to have better intonation is called a compensated bridge. The question is then what is it compensating for?

It's compensating for the amount that the string bends out of tune when it is pressed down -- the string displacement pitch rise. The saddles are moved back (flattened) to compensate for the amount of pitch rise introduced by moving the string onto a fret.

[Wonks]

No, it is as complicated as I said.

But regardless, the fact remains that the guitar bridge/saddles need to be intonated. Otherwise you’d just set up the bridge to be twice the distance from the nut that the centre on the 12th fret is (the nominal scale length).

You can do this on classical/flamenco guitars because of the nature of the nylon strings. They are so much ‘softer’ (probably not quite the right word) than steel that the transition length between non-vibrating and vibrating is so small it can pretty much be ignored for all practical purposes. The extra tension caused by fretting a string is again nominal. Which is why you’ll see almost all classical/flamenco guitars with a bridge at right angles to the strings, located pretty much at the nominal scale length from the nut.

But steel and steel-cored strings need more adjustment. The thicker a steel string is, the greater the extra intonation length is. The thicker a wound string is (for a given string set) the longer the required extra intonation length is.

But for the same diameter solid string and wound string, the solid string will need a greater intonation length than the wound, as the wound construction isn’t quite as ‘stiff’ as the solid string,

If you intonate an electric guitar with a solid G string, you’ll almost certainly find that the G saddle is further back than the wound D string saddle.

On acoustics with either a split bridge (wound + solid strings) or a moulded/cut compensated bridge, the wound G string saddle position will be further forward than the solid B string saddle.

So yes, you need to intonate your electric guitar if you want it to play ‘in tune’* all the way up the neck.

*You’ll never get it perfectly in tune for all keys as all the myriad tuning systems that exist are a compromise to some extent. But intonating will make the higher notes generally sound good enough for most people to be happy (people have different inherent levels of pitch detection and ability to tell if two notes are in tune or not). Not intonating the saddles can sound pretty bad.

[Luke W]

Wonks has already covered this well. But there are a couple of simple points that strike me as being worthy of a mention.

Why would you care how far or close the end of the string is to the neck, since we are only talking about a quarter of an inch of adjustment?

Because the distance between the nut and bridge is the factor that determines whether a string will sound the intended notes when fretted. If that distance is wrong, even by 'only' a quarter of an inch, the intonation accuracy will be compromised — intervals will be incorrect and your octave won't be an octave!

It's compensating for the amount that the string bends out of tune when it is pressed down -- the string displacement pitch rise. The saddles are moved back (flattened) to compensate for the amount of pitch rise introduced by moving the string onto a fret.

It's also compensating for the varying weight/thickness of different strings, which all need to sit at slightly different lengths to remain consistent with each other.

[merlyn]

... in addition, strings are very rarely uniform along their whole length. Almost, but not quite. Small variations in mass/unit length can mean that you may need to intonate after each change of strings.

What strings are you using that are uneven? How are you proposing that moving the saddle would do anything about an uneven string? Move the saddle and the string is still uneven.

I don't think it is as complicated as you are making out and the biggest factor is that fretting a string bends it out of tune.

... It's also compensating for the varying weight/thickness of different strings, which all need to sit at slightly different lengths to remain consistent with each other.

Eh, so that changes the amount the string bends out of tune as you push it down. Or doesn't it? Are you telling me that 12s are as easy to bend as 9s?

[Wonks]

... in addition, strings are very rarely uniform along their whole length. Almost, but not quite. Small variations in mass/unit length can mean that you may need to intonate after each change of strings.

What strings are you using that are uneven? How are you proposing that moving the saddle would do anything about an uneven string? Move the saddle and the string is still uneven.

I don't think it is as complicated as you are making out and the biggest factor is that fretting a string bends it out of tune.

No string is perfect. When tuning the full length of the string you are basically tensioning the average mass/unit length of the string to tune to pitch. When you fret a note (and for intonation purposes we are using the 12th fret) you then use the average mass/unit length of that length of string. On a good string, it may well be the same value, but if there is slight unevenness in the string's diameter or a slight variation in the number of windings per unit length on the wound strings. It's all very small, but if you didn't have small variations, you wouldn't find that if you fit a new set of strings to an electric, that the saddles need to be moved slightly, or that a thicker string saddle might need to be moved ahead of a thinner string saddle (if just slightly).

And it is complicated. It's what Zenguitar believes, it's what Paul Reed Smith states in interviews and its described in several books I've seen, including The Mechanics and Construction of the Acoustic Guitar by Eddie Green.

And please don't point me to any more 'research papers' by US 6th form equivalent students who get it all wrong and can't even get the name of the equipment using correct.

[merlyn]

... When you fret a note (and for intonation purposes we are using the 12th fret) you then use the average mass/unit length of that length of string.

Does that make sense to you? It doesn't make any sense to me. What is using the mass/unit length? How is moving the saddle relevant to that?

And please don't point me to any more 'research papers' by US 6th form equivalent students who get it all wrong and can't even get the name of the equipment using correct.

Not keen on physics, huh? Oh well. Good intonation means that all notes on the fretboard play in tune, not just the 12th fret. I've managed to achieve that on my guitar and I didn't think it was that complicated.

There was a thread where someone thought they had bad intonation on chords but it turned out to be playing technique that was bending notes out of tune. Guitarists may think intonation is more complicated than it is because no matter what they do the guitar is always slightly out of tune due to using light strings and not playing lightly enough.

[Luke W]

Eh, so that changes the amount the string bends out of tune as you push it down. Or doesn't it? Are you telling me that 12s are as easy to bend as 9s?

I'm telling you exactly what I said

Unless I misunderstood, you were saying that moving saddles is solely to compensate for how much strings bends out of tune when you fret a note, which it isn't.

There was a thread where someone thought they had bad intonation on chords but it turned out to be playing technique that was bending notes out of tune. Guitarists may think intonation is more complicated than it is because no matter what they do the guitar is always slightly out of tune due to using light strings and not playing lightly enough.

I'm with you there, to a point. Many such issues can be caused by heavy-handed playing, or in some cases, frets that are sitting too high.

But there's no getting around the fact that moving the saddle is (very slightly) changing the scale length for that particular string, and so directly affects the intonation along said string.

Good intonation means that all notes on the fretboard play in tune, not just the 12th fret. I've managed to achieve that on my guitar and I didn't think it was that complicated.

Yes, but assuming the distance between the frets was set to a tight enough tolerance when the fingerboard was slotted/fretted, getting it right at the 12th fret means that the others should follow suit.

[merlyn]

It's better if you figure this out yourself.

Intonation can be a problem.
The solution is a one parameter solution. (Changing the length of string between the 12th fret and the saddle)
Which means ...

[Drew Stephenson]

[deleted]

[Wonks]

... When you fret a note (and for intonation purposes we are using the 12th fret) you then use the average mass/unit length of that length of string.

Does that make sense to you? It doesn't make any sense to me. What is using the mass/unit length? How is moving the saddle relevant to that?

And please don't point me to any more 'research papers' by US 6th form equivalent students who get it all wrong and can't even get the name of the equipment using correct.

Not keen on physics, huh? Oh well. Good intonation means that all notes on the fretboard play in tune, not just the 12th fret. I've managed to achieve that on my guitar and I didn't think it was that complicated.

There was a thread where someone thought they had bad intonation on chords but it turned out to be playing technique that was bending notes out of tune. Guitarists may think intonation is more complicated than it is because no matter what they do the guitar is always slightly out of tune due to using light strings and not playing lightly enough.

You obviously don't understand it, so there really is no point conversing with you further.

[Luke W]

It's better if you figure this out yourself.

Well, the main thing is that all of my guitars are set up nicely and have good intonation. So I must have already figured it out accidentally.

10+ times in a row. Imagine the chances.

[Albatross]

I always use the old 12th fret harmonic / 12th fret fretted method, never had much trouble with that and I play mostly 12-String acoustics with 12 to 54s.

Must have made a dozen 12-string bridge saddles for those guitars. Always a pita intonating a bone saddle but they all play well.

[Mannyrock55]

Wow! An outstanding amount of great explanations and information.

Thanks to all.

Mannyrock

[BWC]

It's better if you figure this out yourself.

Intonation can be a problem.
The solution is a one parameter solution. (Changing the length of string between the 12th fret and the saddle)
Which means ...

...that it's a simple problem to solve, but that wasn't the question. The question was "why is this necessary?" which is a bit more complicated than you seem willing to accept. What, specifically, has Wonks said that you disagree with?

[BWC]

...one parameter...

Aren't string gauge, formulation, manufacturing tolerance / consistency, action, average finger pressure, etc. also "parameters" that have an effect on intonation?

[zenguitar]

Perhaps it might help if we looked in more detail at why a stringed instrument requires intonation.

It is widely assumed that intonation is needed to compensate for the amount the string is stretched when it is pressed to the fret. But it isn't that straightforward. Yes, the string is stretched and has increased tension as a result. But the increase in string tension is actually quite small and only accounts for a small part of the adjustment actually required.

Also, proportionally, the change in tension from fretting is pretty much the same from string to string. This would suggest that all 6 strings would need similar adjustment. We know from experience that thicker strings require more intonation than thinner strings and this is consistent regardless of the gauges of sets and type of metal used for windings. We need something more to explain this.

Our theoretically perfect string will vibrate very nicely, but once we enter the real world we discover that the strings don't perform according to the theoretical model. We have to account for the limitations of the materials we are using.

Our string is fixed at the saddle at one end, and at the nut or by fretting at the other end. As it is plucked and vibrates it moves from maximum excursion one way then back to maximum excursion the other way. We have to look at what happens to the string at the ends where it is fixed. On the theoretical string there is a perfect transition each time the vibration changes direction. No problem.

However, on the real world string the thickness and stiffness of the material means that it doesn't vibrate in the way the theoretical model describes. Basically, it cannot perfectly transition from moving in one direction to the other direction. Instead, it has to bend between the two extremes.

So, at each end of the string there is a very short section where the material of the string needs a little extra length to account for that bending. But because the ends are fixed it can't get any extra length so instead it steals a little bit from the speaking length of the string. You can think of it as a tiny part of each string that doesn't contribute to the vibrating. And this is the thing that requires intonation to correct.

Here's an example to illustrate, but I will use numbers orders of magnitude too large as that will make the problem clear.

You play the open string and those parts at the end of the string not vibrating make up 1% of the string length. For any string that non-contributing section is a fixed length, it is a function of the material and the thickness and not related to the pitch of the note. If you fret the string at the 12th fret you have halved the length of string, but the non-contributing section remains the same so now it makes up 2% of the string length. This results in the speaking length of the string now being shorter than it should be and sounding sharp.

This why intonation is required.

For the same material, a thicker string is a stiffer string which creates a longer non-contributing section. This will require greater intonation.

This explains the familiar stagger of saddles.

Sorry it has been so lengthy but it's hard to explain without breaking down. I was hoping to find some illustrations online to link to that would have helped but no luck.

There has been some simplification to avoid inharmonicity which can complicate matters further.

Andy

[ajay_m]

Sitting with a morning coffee reading this thread and many thanks to Wonks in particular for such a careful explanation. I learned a lot reading that, despite being a hopeless guitar and bass player (string damping and barre chords seem to be my Achilles heel). So frustrating because if I could barre properly then chord shapes transpose easily. Ah well. At least I can be in perfect tune now even if I can't actually play!

[merlyn]

I've heard that guitars finished with nitrocellulose have better intonation than guitars finished with poly.

... What, specifically, has Wonks said that you disagree with?

Wonks' uneven string thing is complete bullshit. Unfortunately, Wonks seems to be from the when you're wrong, double down school.

Good intonation means that all notes on the fretboard play in tune, not just the 12th fret. I've managed to achieve that on my guitar and I didn't think it was that complicated.

Yes, but assuming the distance between the frets was set to a tight enough tolerance when the fingerboard was slotted/fretted, getting it right at the 12th fret means that the others should follow suit.

They should. But not all guitars do. If the nut is cut too high the intonation can be in at the twelfth fret and out on the lower frets because, guess why? the string has further to travel and bends out of tune more. Moving the saddles won't fix that.

An uneven neck can also mean that the twelfth fret is in and other areas of the neck are out. Moving the saddles won't fix that either, and @Mannyrock was asking specifically about moving the saddles.

To use a one parameter solution the problem had better be reduced to a one parameter problem.

... Aren't string gauge, formulation, manufacturing tolerance / consistency, action, average finger pressure, etc. also "parameters" that have an effect on intonation?

Imagine a see-saw. Moving the saddles to improve intonation is balancing a see-saw. With a real see-saw if we put 1kg on one side it is balanced by 1kg on the other side. Mass balances mass. 1kg can't be balanced by 100Hz. With the compensation see-saw one side is a pitch rise caused by pushing the string down, and the other side is a pitch fall caused by lengthening the string. In practice one side is turning a screwdriver, and the other side is the readout of a tuner.

The variables you listed above are only relevant in so far as they affect the amount that the string bends out of tune when it is pushed down.

Perhaps it might help if we looked in more detail at why a stringed instrument requires intonation. ...

Would that be a stringed instrument like a violin?

Hmm. Seems to be something missing there.

'Intonation' means 'in-tuneness' or we could call it 'pitch accuracy'. It applies to all instruments and all music. To differentiate that from moving the saddles on an electric guitar, we could call moving the saddles on an electric guitar 'compensation'. A violin bridge is ruler straight and doesn't have any compensation.

Maybe turning a screwdriver is complicated for the arts faculty. One turn for string gauge, plus half a turn for the speaking length, plus a quarter of a turn for uneven strings, plus an eighth of a turn because Paul Reed Smith said so, plus a sixteenth of a turn because I don't have a nitrocellulose finish.

[Hugh Robjohns]

Merlyn, check the attitude or check out. There's no place here for the personal abuse you're posting. First and last warning.

[Wonks]

Intonation on a violin is achieved by the fingering hand's finger positioning. Not by any bridge angle.

[Albatross]

This is interesting https://thinkns.com/wp-content/uploads/ ... ctions.pdf if you have one of these...



But even on a standard violin, violinists adgust their bridges for intonation. Its part of the art of the violinist.

[Tomás Mulcahy]

Would that be a stringed instrument like a violin?

Hmm. Seems to be something missing there.

Yea, there is something missing. The thorny issue of temperament*. The violin pictured is not fretted. The player has total fine control over pitch, so they can play in any temperament. Fretted violins (or any fretted stringed instrument) are tuned for equal temperament. This requires accuracy because the frequency ratio is one to the twelfth root of two. There is a limit to the number of decimal places you can measure to on a fretboard, so there is a need for accuracy. With all the other variables Wonks and others have already listed, a way to intonate that does not require files and chisels etc. is essential.

*probably the biggest reason poor players are out of tune is that we naturally prefer just intonation, ET has to be learned. But I am not here to discuss pitch perception

[merlyn]

... The violin pictured is not fretted.

OK, so we've narrowed it down from stringed instruments to fretted stringed instruments that need compensation. If that's the case how do you explain this?